Paraffin wax compositions



Patented Apr. 21, 1953 UNITED STATES OFFICE PARAFFIN WAX COMPOSITIGNSRobert G. Gapell, William Ridenounand John A. Stewart-,Pittsburgh, Pa.,assignors to Gulf Research & Development Company, Pittsburgh, Pa., acorporation of Delaware No Drawing. Application June'fl, 1950, SerialNo; 166,763

6 Glaims. .1 W

This invention relates to improved paraffin wax compositions, and moreparticularly to im-- proved paraffin Wax compositions stabilized againstoxidative and. analogous forms of deterioration resulting fromsubjecting paraifin wax to elevated temperature, air, and the like.

The methods of separating parafiin wax from crude petroleum products,such as by distillatiomchillingwith filtering orcentrifuging,.sweating,and solvent extraction, are well known.Variousmethods of .parafiin wax purification, such as treatment withsulfuric acid and iullers earth, arewell known. Although thispurification helps to produce. morestable paraffin Waxes initially freefrom odor, taste, and color, it is not efiective enough to preventsubsequent oxidativc deterioration which has been troublesome toindustrial users of parafiin wax.

One of the most widely practicedapplications of paraflin wax is in thecoating industry wherein hot wax baths are employed for waterproofing,treating, impregnating. or sizing paper and similar products, andwherein wax is employed to .provide a protective coatingfor materials ofall kinds. More specifically, the use of. hot liquefied wax is widelypracticed in the manufacture of such articles as waxed paper, especiallywaxed bread wrapper, waxed milk carbons and other beverage containers,cartons, bottle caps, shot shell tubes, matches, wax impregnatedfabrics, paper-metal foil electrical condensers, junction and terminalboxes, transformers, wax impregnated insulation, coils and windings,candles, as well as a host of otherproducts too numerous to mention.

In each instance where a hot bath of liquefied paraffin wax is employed,problems of wax decompositionmustbe dealt with. This-decompo sition,which is generally considered tube the result of an oxidative mechanism,is evidenced by therappearance of undesirable od'o'rs, discolorationofthe wax, and the formation of organic acids,.peroxides, and possiblyanhydrides and lactonesin thewax. Thus, suppliers-of re fined parafiinwax generally recommend" that the temperature of a wax melt bekept-belovv160 F. (71C.) because, beginning at about thistemperature,decomposition starts, accompanied by the development of an acrolenic orburnt odor, a similar taste and a darkening of the color. Paraflin waxesranging in melting point from 59 F. C.) to 176 F. (80 C.) having fromfifteen to thirty-five straight chain carbonatoms are readily oxidizedin contact with air above 160 F. By way of example, after 50 hours at 2200 F. a paraifin Wax having a melting point of 122F. begins to showtraces of peroxides, and aften'QU hours at 212 F. a titratable amount offatty acid has developed.

Besides the formation of objectionable odors and an increase in colorand acidity, oxidation brings about a lowering of melting point andti'isilesfingth, and an overau deterioration (if vamable properties Suchas hardness and the like, 0f the wax. Moreover, when decompositionoccurs, much is 1651. through Volatiliz'atioii and the periodicpurification steps necessitated by this" decomposition. consequenu it isof considerable importance to improve the heat stability of para'i'nnwax.

Wax compositions of improved heat stability,

moreover, offer many processing advantages.

Wax coating and impregnating baths may be operated safely at highertemperatures to effect improved'penetration, while allowing bettercontrol over theamount of wax pick up by the paper or other stock beingtreated. In addition, en

tirely' new applications, previously eliminated from considerationbecause of temperature limitations, become practicable for waxes havingimproved heat stability. Furthermore, tank cars may be" unloadedmore-rapidly because higher temperatures resulting'in lower viscositiesgive better transfer of heat andfiow, making possible savings in laborand steanicosts.

A iurther problem encountered by users of paraffin wax is that ofproviding a finished product, such aswaxed paper and beveragecontainers, which will-not deteriorate or discolor upon exposuretoair.Thesalability of food products undesirable" products of? oxidation;However, the.

inhibition of paraffin Wax against an resents special difficulties notencounter choosing an anti-oxidant for other pii ofwithstanding thetemperatures eifipley'ed in wax melts'withoutloss'in anti-oxidantpowers. Thisproblem, and oxidationcdnditions in general;are'acceiituated'in the blending ofiparafiiii wax Witfihigh'r meltingpoint materias Such rposes. First, the anti-oxidant material must becapable as polyethylene, as set forth in copending application SerialNo. 601,556, filed June 25, 1945, by Bowman, Ridenour and Hollenback andassigned to the same assignee as the present application. The highertemperatures and agitation employed tend to increase oxidation.Accordingly, antioxidants which are suitable in mild temperatureapplications may not be suitable in paraflin wax. In addition, ananti-oxidant must not adversely affect the physical properties of thewax.

Where parafiin wax is employed in the manufacture of wrappings,containers, and coatings for foods, an anti-oxidant must not impartcolor, odor, or taste to the wax, either in the wax melt or when incontact with the food. The standards for paraffin wax are generally muchhigher than for most other products including many edible products suchas edible fats and oils. This is particularly true with regard to colorand odor. Lard oil, for example, has a characteristic odor whichalthough not objectionable from a standpoint of human consumption wouldbe highly o'bjectionable if found in parafiin wax compositions. Anycolor imparted to parafiln Wax is highly objectionable from a marketingstandpoint and, therefore, a very small degree of oxidation which mightgive only a slight off-white cast to the wax is undesirable, whereas inpetroleum oils in general and in many food products a slightdiscoloration goes unnoticed. Parafiin wax is essentially odorless and,therefore, any odor due to impurity is very easily detected. Forexample, oxidation of parafiin wax to such a degree that it has aperoxide number of 0.01 is usually enough to confer a definitelydetectable oxidized odor. Such a small amount of oxidation with itsattendant odor may go unnoticed in many other substances which have someslight characteristic odor of their own, the characteristic odor tendingto mask the oxidized odor. Since paraffin wax is a crystalline material,small amounts of impurities can effect relatively large changes inphysical properties such as melting point and tensile strength. Smallamounts of impurities in noncryetalline substances will not exert such anoticeable effect.

The essentially completely odorless and tasteless character of paraflinwax combined with the fact that the oxidationof paraflinic-typecompounds always leads to soluble oxidation products which tend toaffect taste and odor makes the problem of inhibiting parafiin wax onethat is both difficult and unique. The rigid requirements in the tradefor parafiin wax are therefore such that an anti-oxidant for paraflinwax must be effective in very low concentrations where it will not causetaste or odor by itself and at the same time it must, in that lowconcentration, be so effective that the formation of even extremelysmall amounts of odorand taste-producing decomposition products issuppressed.

The question of whether or not any material will satisfactorily functionas an anti-oxidant in any medium is quite unpredictable, for antioxidantaction is highly selective and apparently catalytic. It is so selective,in fact, that one cannot predict with any degree of certainty that amaterial which is a known anti-oxidant .for one substance will stillperform as a satisfactory anti-oxidant in another medium. For example,it is well known that many phenolic materials are useful ananti-oxidants for various purposes, but a wide variety of these phenolicmaterials are not suitable as wax anti-oxidants. To illustrate, a numberof phenolic compounds, known to possess 4. anti-oxidant properties inother environments, have been tested in parafiin wax and found to beunsatisfactory as parafiin Wax anti-oxidants. These compounds are asfollows:

2,2-bis (4-hydroxyphenyl) propane;

1,1-bis (l-hydroxyphenyl) cyclohexane;

Orthodihydroxybenzene; (catechol) Metadihydroxybenzene; (resorcinol) Bis(2-methoxyphenyl) methane;

2,5-ditertiarybutylhydroquinone;

3-pentadecylphenol;

Bis (2 hydroxy 3,5 ditertiarybutyl 6 methylphenyl) methane;

1,1,2,2 tetrakis (2 methyl 4 hydroxy 5 tertiarybutylphenyl) ethane.

Thus, a material which may be found to exhibit anti-oxidant propertiesin rubber, etc., cannot on that basis be expected to exhibitanti-oxidant properties in paraffin wax. Furthermore, it is difiicult topredict that such a material would be otherwise suitable for use in waxcompositions. Apparently, the nature of paraflin wax has considerablebearing on the question.

It is therefore an object of our invention to provide new paraffin waxcompositions having improved stability against general decomposition oroxidative deterioration.

More specifically, a further object of our invention is to provide newparaffin wax compositions of improved heat stability, such as stabilityagainst decomposition in the hot liquefied state.

A still further object of our invention is to provide new paraffin waxcompositions having stability against deterioration due to the action ofair.

Another object of our invention is to provide improved paraffin waxcompositions having good color and exhibiting substantially no odor ortaste, such that they may be employed in food packaging.

These and other objects are accomplished by the present inventionwherein we provide improved paraffin wax compositions comprising a majoramount of a refined parafiin wax and a minor amount, sufiicient toinhibit oxidative deterioration, of 1,1 bis(2-hydroxy-3,5-dimethylphenyl) isobutane having the following structuralformula:

This compound may be produced by methods well know in the art and itisalso known to the art.

We have found that the resistance of paraffin wax to oxidation can bematerially increased, and the temperature to which it may be heatedwithout breakdown can be substantially raised by addition to the wax ofrelatively small amounts of the compound set forth.

This compound can be employed to advantage in paraffin wax stabilizationin amounts ranging from about 0.0001 to 0.1 per cent, by weight, of thewax composition. A preferred range is from about 0.0005 to 0.01 percent, by weight, of the wax composition.

The following illustrative example permits fur-,- ther understanding ofour invention and showsthe advantageous results obtained in a wax com-i.

5. position eontaining. 1,1 bis (2- hydroxy-3,5.-dimethylphenyl)isobutane. For the-purposes of the following: test, a highly refinedparaflin wax having. amelting point of 122 F., as determined by A. S.TIM. methodDB'Y-Z, was employed. The peroxide number, neutralizationnumber and saponification number. referred tohereinafter, are allobtainedby'means ofstandardwell known tests, and are indicative of thedegree of oxidative breakdown of the paraifin wax subjectedto oxidation.

EXAMPLE A blend was prepared employing a 122 F., A. S. TuM. melting.point, parafiin wax andaOlOOl per cent, by weight, of-l,1 bis(2,-hydroxy=3,5-.dimethylphenyl) isobutane. Three hundred (300) grams ofthe blend were placed in a glass oxidation cell suspended in an oil bathmaintained at 240 F. Preheated dry air at a temperature substantiallythe same as that of the wax was passed upwardly through the molten waxat a controlled minimum rate of 1.6 cu. ft. per hour. Once everytwenty-four hours samples were withdrawn and the oxidation stability ofthe wax was measured by analyzing for acidity, peroxides, andsaponfiable material by methods well known in the art. The odor also wasnoted.

The table shows the results obtained along with data on the uninhibitedwax control subanti-oxidant continues thereafter to perform its desiredfunction, and aids link preventing: subsequent deterioration of theparafiin wax due to adverse conditions of heat-air and the like.

The potency as,.a..paraffin..wax anti-oxidant of the compound disclosedherein permits of the employment of hot baths containing the inhibitedparaifinwaxes of this invention. In employing such-baths it is notnecessary to use a paraiiin, wax already containing the anti-oxidantofthis invention, butsthe .anti oxidant can be added in suitableamountto, themolten paraffin wax in thebath in orderto prevent the oxidativedeterioration thereof.

Since the. anti-oxidant of this invention can be employed so efiectivelyin relatively small amounts, it does not affect the odor and taste ofthe paraifin wax with which it is incorporated, and similarly, none ofthe desirable physical properties of the wax, such as melting point andtensile strength are adversely affected.

As will be understood by those skilled in the art, the stabilizedparaffin wax compositions of our invention may contain other additivesand ingredients blended therewith to improve other characteristics, suchas tensile strength, sealing strength, etc., of the composition.

While our invention has been described above with reference to a,specific example and embodijected to the same test conditions. ment, itwill be understood that the invention Table Neutralizationsaponification ggf ygz Number Number mg. KOH mg. KOH wax gm. wax gm. waxDays Oxidized Control Control Control D 115 1) us us Control 0001%Control 0001 Control Q0017;

Additive Additlve Additive It is readily seen that without theanti-oxidant additive of our invention all three measures of oxidativedeterioration, viz., the peroxide number, neutralization number andsaponification number, increased rapidly with time whereas values forthe sample which contained the anti-oxidant showed no change even afterseven days. The initial rise and subsequent drop in peroxide value forthe uninhibited control sample is typical of wax oxidation.

The uninhibited wax developed a strong oxidized odor on the second dayof the test, but the inhibited composition did not develop such an odorfor the full seven days of the run.

The above specific example clearly demonstrates the efficacy, as aparaffin wax antioxidant, of 1,1 bis (2-hydroxy-3,5-dimethylphenyl)isobutane. The complete lack of change in peroxide, neutralization andsaponification numbers, coupled with the lack of odor formation, aftersubjection of the inhibited parafiin wax to severe oxidative environmentindicate beyond any doubt that the disclosed compound is a remarkablyefiective parafiin wax anti-oxidant. Furthermore, it is not onlyefiective for inhibiting oxidation of parafiin wax in the hot liquefiedcon dition, but since the anti-oxidant is retained by the Wax in thefinished wax treated product, the

is not limited by such example and embodiment but resort may be had tosuch modifications and variations as fall within the spirit of theinvention and the scope of the appended claims.

What we claim is:

1. An improved wax composition comprising a, major amount of a paraffinwax and a minor amount, sufiicient to inhibit oxidative deterioration,of a compound having the following structural formula:

aesaooe 7 inhibit oxidative deterioration; a compound havcent, byweight, of 1,1 bis (Z-hydroxY-iS-dting the following structural formula:methylphenyl) isobutane.

' OH ROBERT G. CAPELL.

H WILLIAM P. RIDENOU'R. H30 CH 5 JOHN A. STEWART.

References Cited in the file of this patent UNITED STATES PATENTS 10Number Name Date 5. The method of claim 4, wherein the said 2,515,907Stevens et a1 July 18, 1950 compound is present in an amount from about2,515,908 Stevens et a1 July 18, 1950 0.0001 to 0.1 per cent, by weight.

6. The method of preventing decomposition of OTHER REFERENCES a moltenparafiin wax bath which comprises Phenolic Anti-oxidants for ParaffinicMatemaintaining therein from about 0.0005 to 0.01 per 15 rials,Morawetz, Industrial and Eng. Chem., July

1. AN IMPROVED WAX COMPOSITION COMPRISING A MAJOR AMOUNT OF A PARAFFINWAX AND A MINOR AMOUNT, SUFFICIENT TO INHIBIT OXIDATIVE DETERIORATION,OF A COMPOUND HAVING THE FOLLOWING STRUCTURAL FORMULA: